It has been found that the GTP-binding subunit (alpha-s) responsible for stimulating adenylate cyclase activity (AC) in a variety of cell types is transferred from its membrane complex with hormone receptors and other components (beta, gamma) of the so-called Ns protein(s) in rat liver (RL) and human erythrocyte (HE) membranes to sites on membranes obtained from mouse lymphoma cells lacking the alpha-s subunits (cyc-). Transfer of alpha-s was induced during co-incubation of cyc- membranes with HE or RL by hormones, various quanine nucleotide analogs, or when the donor membranes were treated with cholera toxin and NAD. The implication of these findings is that release of alpha-s may be the mechanism by which hormones and GTP regulate the activity of effector systems such as adenylate cyclase.